Servo control device having automatic filter adjustment function based on experimental modal analysis

Abstract

A servo control device includes: a speed control loop including a speed command generating unit, a torque command generating unit, and a speed detecting unit; a sine wave disturbance input unit; a frequency response calculating unit estimating a gain and phase of speed control loop input/output signals; a resonance frequency detecting unit; a resonance mode characteristic estimating unit estimating resonance characteristics from the frequency response at a resonance frequency and frequencies therearound; a rigid-body mode characteristic estimating unit estimating rigid-body characteristics from the frequency response in a low-frequency band; a filter attenuating a component in a particular frequency band in a torque command; and a filter adjusting unit making setting so that the filter has specified characteristics. The filter adjusting unit further includes a filter adjusting part attenuating a component in a frequency band corresponding to a resonance mode estimated by the resonance mode characteristic estimating unit.

What is claimed is: 
     
       1. A servo control device comprising:
 a speed command generating unit configured to generate a speed command value for a servomotor; 
 a torque command generating unit configured to generate a torque command value for the servo motor based on the speed command value; 
 a speed detecting unit configured to detect speed of the servomotor driven based on the torque command value; 
 a speed control loop configured to include the speed command generating unit, the torque command generating unit, and the speed detecting unit; 
 a sine wave disturbance input unit configured to input sine wave disturbance to the speed control loop; 
 a frequency response calculating unit configured to estimate a frequency response including a gain and a phase of speed control loop input/output signals based on an output from the speed control loop at time when the sine wave disturbance is input to the speed control loop; 
 a resonance frequency detecting unit configured to detect a resonance frequency, at which the gain of the frequency response is local maximum; 
 a resonance mode characteristic estimating unit configured to estimate a resonance characteristic from the frequency response at the resonance frequency and frequencies around the resonance frequency; 
 a rigid-body mode characteristic estimating unit configured to estimate a rigid-body characteristic from the frequency response in a low-frequency band; 
 a filter configured to attenuate a component in a particular frequency band included in a torque command; and 
 a filter adjusting unit configured to make setting of the filter so that the filter has a specified characteristic, 
 wherein the filter adjusting unit further includes a filter adjusting part configured to attenuate a component in a frequency band corresponding to a resonance mode estimated by the resonance mode characteristic estimating unit. 
 
     
     
       2. The servo control device according to  claim 1 , wherein the filter adjusting part makes setting of the filter by expressing the frequency response of the speed control loop by using at least one resonance mode characteristic estimated by the resonance mode characteristic estimating unit and a single rigid-body mode characteristic estimated by the rigid-body mode characteristic estimating unit, comparing energy in the resonance mode and corresponding energy in the rigid-body mode in a particular frequency range, and selecting a mode having a high oscillation possibility in the speed control loop. 
     
     
       3. The servo control device according to  claim 1 , wherein the frequency response calculating unit predicts effect of a filter to be applied according to a mathematical expression, by estimating a transfer function of a transfer mechanism from mode characteristics estimated by the resonance mode characteristic estimating unit and the rigid-body characteristic estimating unit and performing curve fitting on a frequency response curve obtained through experimental measurement, and displays an obtained result as a Bode plot.